Chemical analyzer with automatic calibration

Abstract

Improved apparatus for automatically calibrating and verifying the calibration of a chemical analyzer of the type which determines the concentration of a component in chemical or biological samples, e.g. concentration of glucose in blood or urine, wherein a sample changer sequentially advances samples into position for analysis. Calibration of the analyzer is performed by measuring a calibration standard of known concentration and generating a conversion factor therefor which converts the measured value of the standard to the known value thereof. Means is provided for storing conversion factors and proper calibration of the analyzer is verified by comparing successive conversion factors. If the compared conversion factors differ by more than a predetermined amount, the sample changer is halted and the calibration standard is remeasured. Measurement of the calibration standard is repeated until either two successive calibration factors are generated which differ by less than the predetermined amount, or until a predetermined number of unsuccessful measurements are made at which time the analyzer is stopped.

1. Improved calibration apparatus for use in an automatic analyzer of the type which measures a characteristic of a plurality of samples and includes sample changer means adapted to advance said samples in sequential fashion into position for analysis, the sample changer means further adapted to intermittently position for analysis calibration standards having a known predetermined value of said characteristic, the improved calibration apparatus comprising: measuring means for measuring said characteristic of said calibration standards and generating electrical signals indicative thereof,   conversion means responsive to each measurement of a calibration standard for generating a conversion factor which converts each electrical signal to said predetermined value of said calibration standards,   storage means for storing said conversion factor,   verification means for verifying the calibration of said analyzer upon each analysis of a calibration standard including means for comparing the conversion factor generated for the calibrated standard being measured with the stored conversion factor for the previously analyzed calibration standard and for generating a control signal if the compared conversion factors differ by more than a predetermined amount,   sample changer control means responsive to said control signal for halting advancement of the sample changer means to maintain the calibration standard being measured in position for remeasurement, and   means for energizing said measuring means to remeasure the calibration   
     
     
       2. The improved calibration apparatus of claim 1 further including means for monitoring the remeasurement of the calibration standard and for stopping operation of said analyzer after a predetermined number of 
     
     
       3. The improved calibration apparatus of claim 1 wherein said verification means compares the conversion factor generated for the calibration standard being measured with a preset conversion factor if no stored conversion factor is available from a previously analyzed calibration standard.